Design and Evaluation of Additively Manufactured Gas Turbine Ring Segments with In-Wall Cooling Schemesvon Thomas Wimmer
A ring segment for the first row of a large gas turbine was designed with a novel cooling scheme viable only through Additive Manufacturing (AM). The macro cooling channels used are wavy rectangular channels which increase the heat transfer. The cooling channels are embedded in the heat-loaded wall. The additively manufactured ring segment (AMRS) was manufactured and tested in a full engine test.
The numerical model uncertainty was investigated in detail including manufacturing uncertainties. Experimental data agreed well with the numerical models. Within the full engine test, the AMRS was compared to a conventionally manufactured ring segment. The AMRS outperformed the conventional ring segment in terms of cooling consumption and metal temperatures.
After the engine test, the AMRS was cut up to make a vast number of the cooling channels accessible for geometrical measurements. Additionally, their friction factors could be determined experimentally. A cold flow test rig was developed to determine friction factors of single macro channels with an accuracy of about 10%. It allowed a quantification of the Laser-Powder-Bed-Fusion (L-PBF) process’ accuracy.
A numerical design method specifically for In-Wall cooling schemes in gas turbine parts has been developed. It was tested for the same ring segment as the AMRS. The design method was used to perform a parameter study on several In-Wall cooling schemes. The general advantages and design recommendations for such cooling designs have been derived. Additionally, the design method was extended to include a local wall thickness adaptation method which decreases the thermal gradients in the part.
Overall, the advantages of AM In-Wall cooling schemes for gas turbine parts were shown on an exemplary ring segment. The capabilities of the L-PBF process to produce complex macro channels have been quantified. A design method which reaps the benefits of AM has been developed.